Allow the students to use their calculators. Students should be able to see that the yellow square in the middle is the actual perfect square because all four sides are equal. Call on a volunteer to verbally state how he/she found the answer.

Address the class and state ...

"YOU HAVE FOUND THAT √20 IS EQUAL TO 2√5 . CAN YOU DEMONSTRATE THAT THE EXPRESSIONS ARE EQUAL WITHOUT CALCULATING THEIR DECIMAL EQUIVALENCE?"

Tell the students to discuss their thoughts with their elbow partner. Depending on how much the students are struggling, I may or may not hint them by writing the property addressed in the previous lesson on the board: √a ∙ √b = √ab.

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Big Idea:
Temperature is the measurement of the average energy of particles in a system. but just how fast are they moving? Faster than a speeding car? Faster than the speed of sound? Faster than the speed of light?